Considerable efforts have been undertaken to accelerate the breakdown of existing anthropogenic petroleum hydrocarbons (PHCs) by appropriate in situ remediation technologies. In situ phytoremediation, using higher plants to remove, stabilize, degrade, and/or metabolize hazardous contaminants, has emerged as a promising green technology for cleaning up environments contaminated with PHCs. Weed plants are generally considered to have great potential for use in phytoremediation due to their extensive fibrous root systems and relatively robust characteristics, thus helping establish a strong rhizosphere through contaminated soils. In this review, some important mechanisms involved in phytoremedation of PHC contaminated soils, including phytoaccumulation, phytostabilization, phytodegradation, phytovolatilization, and rhizodegradation, were summarized and discussed. In recent years, a large number of laboratory approaches have been developed to further enhance the phytoremediation efficiency of PHC contaminated soils. The success of these laboratory studies has encouraged researchers to attempt phytoremediation of PHC contaminated soils in the field. However, many limitations still exist in order to successfully apply laboratory experiments to trials in the field.